The present invention relates generally to improvements in cameras and it relates more particularly to an improved mechanism for automatically deactuating an electric motor driven film advance upon reaching the end of the film.
It is well known that in an electric motor driven film take-up mechanism, first a predetermined number of film frames is indexed in a frame number dial, and when the number of exposed film frames reaches the set value, the current supply circuit to the motor is opened to effect an automatic stop. When the number of frames is smaller than the value set in the frame number dial, the stop is not effected until the set value is reached through the performance of a series of actions or of partly omitted actions. Therefore, it is desirable to perform an automatic stop consequent to some change in operation, such as the halting of the take-up shaft owing to exhaustion of the film so as to protect the camera, the take-up mechanism and the film.
There are generally two types of automatic film take-up means; one in which the coupling section to the camera rotates by a predetermined angle for an increment film take-up action and the take-up action is then stopped, and the other in which a slip coupling is provided in the transmission system between the take-up shaft and the drive motor and take-up action is carried out until the take-up shaft is stopped.
Generally, film take-up and make-ready action consists of the following actions: (i) film take-up action (ii) make-release-ready and release action (iii) release retention and return action (iv) idle rotation action for making ready for take-up action. It is well known that in the aforementioned slip coupling type, when the film is exhaused the (i) film take-up action is omitted and the action (ii) - (iv) are repeated, and that in this case the film is forced to stop so that an undesirable influence is exerted on the camera mechanism with its consequent drawbacks and disadvantages.